HOT WEATHER CONCRETING – 10 GUIDELINES TO FOLLOW

The followings are general recommendations or considerations for hot weather concreting.

Liquid Nitrogen Used To Keep Mixer Cool
Liquid Nitrogen Used To Keep Mixer Cool

Guidelines to Follow

1. Do not exceed the maximum allowable water-cementious materials ratio or the manufacturer’s maximum recommended dosage of any admixture.
2. Consider retarding admixtures if their performance has been verified during trial batches.
3. Substitute ground, granulated blast furnace slag for part of the Portland cement. These materials hydrate more slowly and generate lower heats of hydration than cement, reducing tendencies toward slump loss, premature stiffening, and thermal cracking. Fly ash with high calcium and aluminum contents may cause premature stiffening.
4. Low air contents can be corrected by increasing the dosage of air-entraining admixture. Better or longer mixing may allow maintenance of a constant air-void spacing factor without a greater air content. Using additional water reducer may also be helpful.
5. Risk of early-age thermal cracking is reduced by ensuring that the temperature of the plastic concrete is as low as practical. This can be done y following ways
a. Sprinkling with water may cool aggregates; be sure to      correct for the aggregate moisture.
b. Aggregates need to be batched in a saturated surface-dry   condition to avoid absorbing mixing water.
c. Chilling the mixing water or adding chipped ice in substitution for some of the water lower the mix temperature. Be sure that all of the ice melts during mixing.
6. Consider painting the mixing and transporting equipment white or another light colour to minimize the heat absorbed from the sun.
7. In extreme conditions, consider scheduling concrete placements for during the evening or night.
8. In case of construction of rigid pavement, moisten the base before the concrete is placed to keep the temperature down and keep it from absorbing water from the concrete.
9. Place and finish the concrete as rapidly as possible to apply the curing compound at the earliest possible time. The use of a white curing compound will reflect the sun’s heat. If there is any delay in applying the curing compound, use a fog spray or evaporation retardant to keep the surface from frying out.
10. Refer to IS-7861-Part-1, Recommended Practice For Hot Weather Concreting, for additional information.

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